汽车用金属板材冲击拉伸响应性能的试验研究

Test of Tensile Impact Response of Automotive Sheet Steel

介绍了一种在仪器化摆锤冲击试验机上对矩形板材试样实施冲击拉伸并评价材料动态响应特性的宝钢单杆试验方法。基于试验输出的力—位移—能量曲线,探讨了某车用软钢在102/s应变速率水平时的动态强度、塑性与韧性性能。根据摆锤冲击试验直接测量势能变化得到的冲击吸收功,可对动态应力—应变曲线加以确认与标定,提高了强度性能评价尤其是抗拉强度的量值可靠性,而由曲线标识出的断裂点应变亦可通过测量试样的断裂延伸率加以确认。试验表明针对文中选用的材料,加载应变速率由10-3/s提高至102/s并未对材料的强塑配备产生显著影响,即材料的拉伸破断吸收能保持稳定。而3%预应变诱发的形变硬化效应却显著降低了材料在动态载荷条件下的延塑性特征,使材料更易表现出失稳断裂的趋势。

＂Baosteel One Bar method＂ i. e. BOB method is introduced based on the response properties of a piece of rectangular automotive sheet steel on the pendulum instrumented impact tester. In view of the output forcedisplacement-energy curve, the dynamic strength, plasticity and toughness properties of a kind of soft steel for automobile were discussed at the 10^2/s strain rate. The metrologieal certainty of the dynamic tensile strength was strongly relied on the accuracy of stress-strain curve, which could be validated and calibrated by the directly measurement of impact energy from the pendulum dial reading. In addition the total strain at tensile rupture could be verified by measuring the gauge elongation of the broken specimen. It is shown for the sheet steel as studied that the combination of strength and plasticity, implied by the uniaxial tensile rupture toughness, E, can maintain stable, even when the strain rate changes from the 10^-3/s up to 10^2/s level. Whereas the deformation hardening effect induced by the 3% pre-strain has the significant influence on the degradation of dynamic plasticity, which leads to the reduction of tensile rupture toughness under the dynamic tensile loadings.